Saros (astronomy)

The saros is a period of exactly 223 synodic months (equal to approximately 6585.321 days). There is an approximate saros cycle which has been used since ancient times to predict both lunar eclipses and solar eclipses. One saros period after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle. The name "saros" (σάρος) was applied to the eclipse cycle by Edmond Halley in 1686.

Quotes

• The texts are most probably from Babylon, although their exact provenance is unknown ... All concern luni-solar phenomena with the exception of a text on the last visibility of Mercury, which is found on one side of a tablet whose other side deals with lunar eclipse magnitudes and longitudes.
  The texts fall into two groups. One comprises what we have called "Saros Cycle Texts," which give the months of eclipse possibilities arranged in consistent cycles of 223 months (or 18 years). Three of the four texts in this group concern lunar eclipse possibilities; the other treats solar eclipse possibilities analogously. Included in this group is B.M. 34597, known as the "Saros Canon," which we republish to correct several errors in previous publications, and to clarify its structure.
  The second group of texts contains astronomical functions.
  • Asger Aaboe, John P. Britton, Janice Adrienne Henderson, Otto E. Neugebauer, Abraham J. Sachs, "Chapter 1. Introduction". Saros Cycle Dates and Related Babylonian Astronomical Texts. Transactions of the American Philosophical Society, Volume 81, Part 6. Philadelphia: American Philosophical Society. 1991. p. 1. ISBN 978-0-87169-816-2. 

• This article presents a new concept to illustrate the chain of solar eclipses in accordance with the Saros cycle. Eclipses in a Saros cycle are placed in a circle depending on the calendar date. By concentrically placing several Saros circles in chronological order, we notice that the Saros series appear in the form of spirals that resemble a rosette. In an entire Saros series we can easily notice where it begins and ends. By analyzing within the rosette representation the chain of eclipses – circular, radial, and spiral – we can highlight several cycles of eclipses. A correlation between the Saros cycle and the Maya cycles of repeating eclipses is also illustrated.
  • Dimitrie Olenici, (2020). "The Rosette of Spiral Diagrams as Produced by The Saros Series of Solar Eclipses". Romanian Astronomical Journal 30 (2): 121–134.

• The discovery and use of the Saros, a lunar cycle of 18 years and 10 or 11 days, is reviewed from its earliest origins two millennia ago to the present day, when it is known with precision and enables the accurate prediction of both time and type of solar and lunar eclipses. The theoretical basis for the Saros is discussed, along with other historically known lunar cycles. The geometry of the Sun-Moon-Earth system is found to repeat itself after one Saros, not only at eclipses but also at any phase of the cycle, indicating that the Moon moves in a nearly periodic orbit. The search for periodic orbits using the Saros has led to the discovery of a set of eight periodic orbits of period equal to one Saros whose time evolutions closely resemble that of the real Moon. Finally, the potential of the Saros in studying the dynamics and stability of the Earth-Moon system is examined and the existence of other Saros-like cycles of longer periods in the present, past and future of the Earth-Moon-Sun system is explored.
  • Bonnie Alice Steves, (1997)"The cycles of Selene". Vistas in Astronomy 41 (4): 543–571. DOI:10.1016/S0083-6656(98)00004-X.

External links

• Encyclopedic article on Saros (astronomy) on Wikipedia
• The dictionary definition of saros on Wiktionary